Worldwide production of engineered nanoparticles is expected to grow from 2,000 metric tons to 50,000 metric tons over the next decade. New industrial processes must be introduced into the workplace to accommodate this growth. Although studies have shown some nanoparticles to be toxic, methods to assess personal exposure do not exist. Knowledge of personal exposure may be particularly important for such small particles because their concentration tends to decay rapidly with distance from a source. The immediate objective of this Career Development Award is to allow Dr. Thomas Peters to make a successful transition to an independent investigator in the field of occupational and environmental health, with emphasis on protecting the health of workers from exposure to nanoparticles. In the research component of this award, Dr. Peters will conduct laboratory studies to evaluate the precision and accuracy of methods developed by his research group to assess personal exposure to nanoparticles. These methods will then be used to investigate the extent to which workers are exposed to engineered nanoparticles in a facility that produces and handles them. Mixed models will be used to identify the determinants of exposure, while controlling for the between-worker (spatial) and within-worker (temporal) variability. Computer controlled electron microscopy with energy dispersive X-ray detection will be used to further characterize the samples collected in the field study by size, composition, and morphology. These data will be used to apportion exposures to sources. The research proposed in this application is significant because it will enable direct assessment of personal exposure to nanoparticles on time scales relevant to potential acute and chronic adverse health outcomes. As an outcome of these studies, an understanding of exposures will help to prioritize studies in toxicology, epidemiology, and engineering controls to better protect workers. This research component will be complemented by a vigorous career development plan, which will include: (1) formal training in responsible conduct of research, epidemiology, and electron microscopy;(2) regular meetings with the sponsors of this award;(3) participating in group meetings and departmental seminars;(4) presenting results at scientific meetings;and (5) publishing results in peer-reviewed journals. It is envisioned that the multidisciplinary team of sponsors will play an active roll in both the research and career development component of this award.